Color photographic material

ABSTRACT

COLOR PHOTOGRAPHIC MATERIAL UTILIZING THE SILVER-DYEBLEACH PROCESS WHICH HAS HIGH CAMERA- OR PRINTING-SPEED TOGETHER WITH HIGH FASTNESS TO LIGHT AND MOISTURE AND EXCELLENT SHARPNESS PECULIAR TO THE SILVER-DYE-BLEACH PROCESS AND WHICH COMPRISES AT LEAST TWO SETS OF A COMBINATION OF SUPERPOSED MULTILAYERS SAID COMBINATION CONSISTING OF (A) A PREFOGGED LOW-SPEED CHLORIDE-RICH SILVER HALIDE EMULSION LAYER CONTAINING BLEACHABLE DYES, (B) A COLORSENSITIZED OR NON-SENSITIZED HIGH SPEED BROMIDE-RICH SILVER HALIDE EMULSION LAYER, AND (C) AN INTERLAYER OR OVERLAYER SUPERPOSED ON TOP OF THEM, THE COLOR OF THE DYES INCORPORATED IN THE PREFOGGED LOW-SPEED EMULSION LAYER PROPERLY MATCHING THE COLOR SENSITIVITY OF THE HIGH-SPEED EMULSION.

UnitedStates Patent ()flice 3,764,331 Patented Oct. 9, 1973 3,764,331 COLOR PHOTOGRAPHIC MATERIAL Yasushi Ohyama, Takatsuki, and Sadayuki Miyazawa,

Kyoto, Japan, assignors to Mitsubishi Paper Mills, Ltd.,

Tokyo, Japan a No Drawing. Filed Oct. 23, 1970, Ser. No. 83,676

Int. Cl. G03c 1/40 US. Cl. 96-73 1 Claim ABSTRACT OF THE DISCLOSURE Color photographic material utilizing the silver-dyebleach process which has high cameraor printing-speed together with high fastness to light and moisture and excellent sharpness peculiar to the silver-dye-bleach process and which comprises at least two sets of a combination of superposed multilayers said combination consisting of (a) a prefogged low-speed chloride-rich silver halide emulsion layer containing bleachable dyes, (b) a colorsensitized or non-sensitized high speed bromide-rich silver halide emulsion layer, and (c) an interlayer or overlayer superposed on top of them, the color of the dyes incorporated in the prefogged low-speed emulsion layer properly matching the color sensitivity of the high-speed emulsion.

This invention relates to a color photographic material utilizing the silver-dye-bleach process. More particularly, the invention relates to high-speed color prints having the high fastness to light and moisture and excellent sharpness peculiar to tthe silver-dye-bleach process, and which comprises at least two sets of a combination of superposed multilayers coated upon a support, said combination consisting of (a) a pre-fogged low-speed chloriderich silver halide emulsion layer containing bleachable dyes proximate to the support, (b) a color-sensitized or non-color-sensitized high-speed bromide-rich silver halide emulsion layer coated over (a); and (c) an interlayer or overlayer superposed on top of them, the color of the dyes incorporated in the prefogged low-speed emulsion properly matching the color sensitivity of the high-speed emulsion.

This combination of the superposed three layers may sometimes be referred to herein as an element.

The theory of the photographic process generally known as the silver-dye-bleach process is described, for instance, by Friedman in Color Photography," Chapter 24, pages 405-429, 2nd edition, 1968, Focal Press Ltd., London. As for examples disclosed in the applicants Japanese patent application No. 10661/65, the silver-dye-bleach process involves at first coloring silver halide emulsion layers of photographic materials uniformly with suitable dyes usually before exposure, and after suitable exposure, the material is developed with usual black-and-white developer, and after development the material is subjected to the action of a special bleaching bath which bleaches the dye in the emulsion layer with the aid of the metal silver particles of the image as catalyst, whereby the dye is destroyed and bleached in the form and shade of the silver image to produce a reversal color image.

When the subtractive process is used in color photography using three primary colors, it is necessary to dye emulsion layers in colors complementary to those to which the respective layers are sensitive, for instance a green-sensitive emulsion layer in the complementary magenta, a red-sensitive emulsion layer in the complementary cyan, and a blue-sensitive layer in the complementary yellow. Hence deep black is not developed, unless the emulsion layer is dyed deep enough. But when it is dyed deep, as the dye itself absorbs light to which the emulsion layer is sensitive, not only the sensitivity of the emulsion is markedly impaired, but also the light is difiicult to transmit deep into the emulsion layer, bringing about the softer gradation as if the emulsion would become soft. As silver images are difiicult to form at the deepest part of the emulsion layer, the dye remains there after processing, making it difiicult to obtain pure White.

There are many dyes which give such adverse effects as desensitization or chemical fogging to the emulsion layer when added to light-sensitive emulsion layers. There also are some dyes react with the protective colloid such as gelatin and tend to precipitate it, or to increase its viscosity extremely, or to harden it. And other types tend to impair the physical properties of the emulsion layer, and the layer is often loosened during processings. Accordingly the choice of suitable dyes which may be safely introduced into the emulsion layer is very limited.

But it is difiicult to separate an emulsion layer from a dye layer, because bleaching cannot be effected theo retically in the aforementioned process unless silver images which act as a catalyst are present in the dye layer. To overcome this difiiculty, it has been considered hitherto that the only effective way would be to choose dyes which do not produce adverse side effects and use conjointly effective additives which improve the physical properties of the layer, together with some slight shifting of the wavelength relation between the color sensitivity of the emulsion and the color of the aforementioned dyes which must theoretically be in complementary relation.

The applicants first successful trial in separating a light-sensitive layer from a dye layer is described in the applicants Japanese patent application No. 10661/6-5, in which the silver complex diffusion transfer reversal process is utilized in combination with the silver-dye-bleach process.

This process has superior characteristics in itself, but has disadvantages in that the finished prints tends to have harder gradation and the tonal range of the half tone is sometimes very short.

And in this process dyed layers contain as neuclei for the reduction of the silver complex minor amounts of heavy metal or noble metal colloids which are not only difficult to remove after the treatment, but also act as concentration specks for stain, thus impairing the pure White of the prints.

These drawbacks have been removed in the present invention which utilizes another transfer reversal process that excels the silver complex diifusion transfer process in tonal gradation.

The novelty and advantage of the present invention lies in this novel combination of the transfer reversal process with silver-dye-bleach process. According to the present invention, a combination consisting of three superposed layers is used as a unit, which comprises (a) a prefogged low-speed chloride-rich silver halide emulsion layer containing a bleachable dye as a bottom layer, (b) a color-sensitized or non-color-sensitized high-speed bromide-rich silver halide emulsion layer superposedly coated as middle layer upon the layer (a), and (c) a plain binder layer superposed as a top-layer and which may serve as an inter-layer for another combination of these layers (a), (b), (c), or an overlayer of the multilayer materials thus coated comprising at least two sets of the combination.

During exposure, latent images are produced in the emulsion of a middle layer, and during development of the latent images, bromide ions are diffused away from the middle layer (b) into the adjacent bottom layer (a), preventing the development of prefogged chloride rich emulsion, which is otherwise to be developed uniformly making silver images throughout in the deyed layer.

Consequently after bleaching, the dye will remain in the part of the bottom layer where the blackening of the from the middle'layen-and as the-amount of the bromideions is just proportional to the latent image in the middle layer, densities of the final dye images are just proportional to the light which'attacked. the sensitive (high speed) emulsion (b)- v The process of the inveintion is therefore characteristic of a color-negative nature in contrast with the conventional silver-dye-bleach process which is-characteristic of a color-positive nature.

Moreover, the conventional silver-dye-bleach process is the so-called residual process wherein the residue of coated dye obtained by substracting an amount of dyes proportional to an amount of exposure to the emulsion layer constitutes coloration, and any defect or unevenness of the coating thickness of the emulsion (and dye) layer remains as it is.

On the other hand, in the process employed in the present invention, the dye remains only at that part which is proportional to the amount of attack of the emulsion during exposure, and the densities of the color image are exactly proportional to the amount of exposure as mentioned before.

And the finished color image is theoretically free from any defect resulting from unevenness of the coating thickness, and the production of such a photographic material becomes far easier.

This idea of coating 21 prefogged emulsion layer adjacent to a light-sensitive emulsion layer and thereby obtaining an image reversed in black-and-white densities is not a new one.

Nevertheless, it has never been practical in black-andwhite photography, because the developed silver images in both layers appear in superposed condition and the densities are reversed with respect to each other and, the resultant reversed (positive) image has a very dull appearance.

The removal of the light-sensitive (negative) layer in some way or another is therefore necessary after the treatment.

This process, therefore, has found little practical applications except in a copying process similar to the diffusion transfer, in which a light-sensitive emulsion layer is coated on a separate support, treated by close face-toface contact with a prefogged emulsion layer, and then stripped cit.

In such a copying process, the reverse image obtained is a residual image, and the unevenness of the coating appears as it is. Thus, practical attention has never been paid to this process.

It has now been found that the application of this neglected process to the silver-dye-bleach process leads to the elimination of the aforementioned defects. When this reversal process is applied to the silver-dye-bleach process, the resulting image is not a residual image, but the densities of the color image are exactly proportional to the amount of exposure.

In addition, the silver image formed by combining a negative and a positive in the two superposed emulsion layers completely disappears, and the undeveloped silver halide is of course removed by fixation. Hence, there remains nothing which may cause stain or contamination, and white margins remain pure white. I

The prefogging, of the low-speed chloride-rich silver halide emulsionlayer coated as a bottom layer of the combination may be efiected by any known method. Although it is possible to fog the emulsion layer by exposure to actinic light, chemical treatments are employed in general since the former methods have many troubles in mass-production. I

Examples. of the known fogging methods include the addition of suitable amounts of reducing agents such as formalin, ammonia and hydrazine, or sulfurizing agents such as sodium sulfide, thioacetamide and thiourea derivatives, the addition of colloidal silver or collidal silver sulfide which coiistit utes itself a 'developing nuc eus, or

combined-use of these two methods. WW 7 w It is necessary that the relatively high-speed silver halide emulsion used in accordance with the present invention should be rich in silver bromide; and that the prefogged low-speedemulsion should be rich in silver jchloride.

It is considered that bromide ions generated at the time of reduction" of the silver bromide grains in the upper emulsion layer may diffuse into the lower emulsionlayer and may reach the surface of grainslof thesilver chloride and thereby may form silver bromide onthe surface.

It is therefore readily seen that certain limitations of,

the constitution of the silver halide grains in bothlayers should be set. In fact, definite limitations are difficultto set, and it is important to choose proper. oombinations of the two sorts of emulsions by experiments.

It is well known that high resolving power and sharpness are among the characteristic features of the conventional silver-dye-bleach process. These characteristics come from the fact that a high concentration of dye, the

color of which is complementary to the sensitivity of the emulsion, in the emulsion, acts as an irradiation preventing agent and prevents the scattering of light radiated into the emulsion. y i t For this purpose only, however, a high concentration of the dye is not necessary, and suflicientdensity of the dyestuit for this purpose is only about 0.3-0.5,as measured by a complementary filter. 1 7 The dye is required to be dissolved away by diffusion or to be bleached. As will be illustrated in the examples shown hereinbelow, the addition of a dye to a light-sensitive emulsion layer for this purpose i s expected iolincrease the sharpness, although reducing the sensitivity more or less. But theaddition of such an irradiationepreventing dye is not essential in the present invention. According to the present invention, immediately below a light-sensitive emulsion layer is coated a prefogged chlo ride-rich silver halide emulsion layer mixed densely with a bleachable dye which is the complementary colorof the color to which the emulsion layer is sensitive. Thus, this pre-fogged layer acts as the strongest; anti: halation layer for thelight-sensitive emulsion layer on top of it, and it is possible to increase theresolving power and sharpness without reducing the sensitivity of the ,light-. sensitive layer. I

Color prints obtained by the colormaterials of the in: vention have high fastness to light and moisture and excel-. lent sharpness, all of which are the inherent merits o i the silver-dye-bleach process, without involving those drawbacks of severe desensitization, dull gradation-orjreduced stability of the emulsion, all of which come from the in trodution of the dyestufifs at highconcentration into the emulsion layer.

Furthermore, the ill effects of the unevenness of coating, from which the conventional silVer-dye-bleach process cannot be free because of being a residual process, are obviated by the present invention. According to the present invention, a superior color material can be provided which is suitable for making positive prints from acolor negative simply and rapidly without involving any, influericeof the unevenness of the coating and at the same. time Without the need the elaborate and cumbersome treatments of a reversal development.

inhibitthe develop a binder such as gelatin between two superposed lightsensitive layers so as to render either of these light-sensitive layers so as'to render either of these light-sensitive layers free from the influences of the development of the other layer; With commercially available photographic materials utilizing chromogenic development, the main purpose of an' interlayer is to prevent the migration of intermediate' oxidation products of developing agent formed during development'of either of the light-sensitive emulsion layers, from one layer to the other adjacent layer while such still have coupling power, and may form a color image dilferent from the intended one in the adjacent emulsion layer. If an interlayer having a certain thickness is'interposed between these layers, the migration of the oxidation intermediate decreases exponentially, and becomes extinct during its passage through the interlayer. Usually, 'a special substance for preventing such diffusion is not needed. Sometimes, however, methods of preventing color mixingmay be carried out by adding a specific coupler which will be coupled with the intermediate oxidation products but which gives an unstable color which is readily decomposed, or escapes from the layer into the treating solution by diffusion.

'In the present invention, the bromide ion generated by the development of a specific light-sensitized emulsion layer diffuses'not only into the intended pre-fogged emulsion layer of the combination coated immediately upon its underside, but also in the upward direction. If there is no interlayer, thedevelopment of the pre-fogged emulsion layer of anyothercombin'ation of, layers situated above thecombination under consideration is also inhibited, and a color image'of a color, different from the intended one, could appear in the other combination. Thus, color mixing could occurin the same way as in thecase of usual multilayer materials using chromogenicsdevelopment. The intention of providing an interlayer in the present invention is to'prevent this undesirable color mixing. Images of bromide ion could become diffused and would be diluted into the developing solution and finally would diffuse away travelling through the interlayer. Even if the bromide ion reaches the pre-fogge'd emulsion layer above, the effect would be a reduction in thespeed of development, and usually, its concentration in the upper pre-fogged layer is not sufiicient'to prevent the blackening of the pre-fogged layer. Hence, if an interlayer of a certain thickness of plain binderis provide, there is no fear'of color mixing except at a part where the concentration of bromide ion is especially high. Positive means for preventing the color mixing there do exist. If a silver chloride emulsion of suitable concentration is added in the interlayer, all the bromide ions are converted here to chloride ions which are hardly capable of inhibiting development The employment of this method ifs decided by considering the extent of color mixing involved and its economy. Generally, the use of an interlayer containing no silver chloride and having a certainpredetermined thickness is economically advantaigeous Butwhere a very stringent color reproduction is required, it is preferred to incorporate a silver chloride emulsion into the interlayer. It is obviously advantageous to secure highsensitivity 'and clear sharpest image that the types of silver chloride emulsion be selected which are almost transparent to visible'light and with the smallest available grain size, because the silver chloride grains of such a fine emulsion have'a large surface area Which is most effective to prevent the dilf usion 'of bromide ions. In this case, thesilver chloride'emulsion may either be prefogged or be un'-treated for the purpose. The silver chloride emulsion has an advantage'of' bringing about good color separationsince it: has a'strong absorption at the near ultra violet toith e blue-purple portion of the spectrum, and reduces theinherent sensitvity of the sensitive emulsion underlying the interlayer.

The invention will be more specifically described by the following examples, which are intended to be illustrative rather than limitative.

EXAMPLE 1 Two grams of an aqueous solution of hydrazine hydrate diluted with 10 ml. of water is added to 1 kilogram of a gaslight emulsion (containing 20 g. of silver halide calculated as AgNO consisting predominantly of silver chloride and a minor amount of silver iodobromide, generally used for contact paper and the mixture is stirred well thereby to fog the emulsion chemically. The fogged emulsion is then worked with water to remove the excess fogging agent. After remelting the emulsion, 1.0 ml. of 1% mercapto benzothiazole solution is added as a stabilizer, then it is well mixed and cooled for storage. Since the emulsion is originally a low-speed emulsion chemically fogged by the above procedure, it is quickly blackened in a developer. This pre-fogged emulsion is to be used as an (a) element for the color materials of the present invention in combination with a high-speed bromide-rich silver halide emulsion (b). The pre-fogged emulsion so obtained was not substantially sensitive to the amount of exposure suitable for printing the high-speed emulsion.

EXAMPLE 2 As the light-sensitive high-speed emulsion (b), a colorsensitized emulsion consisting predominantly of silver bromide, containing minor amounts of silver iodide and silver chloride generally used for enlarging paper is suitable. One example of the formulation is as follows:

Solution (A) Solution (B) at room temperature (25 C.) is poured into solution (A) maintained at 50 C., and immediately 50 g. of gelatin is added. The mixture is ripened for 30 minutes at 45 C., neutralized with citric acid to pH of 6.0, out to pieces, and washed with water. After the washing, 20 g. of dry gelatin, 3 ml. of 1% potassium iodide solution and 5 ml. of 1% potassium bromide solution are added to the emulsion, followed by second ripening for 60 minutes at 50 C. and adjusting its pH to 5.0 with citric acid. The resulting emulsion is cooled, and stored.

EXAMPLE 3 Five grams of aminoguanido-dialdehyde starch (as described in Japanese patent publication No. 7754168) as mordant and l g. of purified Chicago Blue 6B (CI 24410) are added to 1 kg. of the pre-fogged silver chloride emulsion prepared in Example 1. The mixture was applied in an amount of about 1 g. /m. calculated as of about 50 g./m. Thus there is obtained the first set of a combination of superposed multilayers which is redsensitive and blue-green colored. On top of the first set of the combination is superposed a second set of a multilayer combination consisting of a green-sensitive highspeed emulsion and a magenta-colored pre-fogged chloride-rich emulsion. The latter is prepared with the same procedure as described above except that Diamine Rose (CI 15080) is substituted for the Chicago Blue and both emulsion layers are coated with an interlayer of gelatin.

It is preferred that 0.3% aminoguanido dialdehyde starch solution and about 0.1% of a bleachable yellowish orange acid dye of the following structure,

should be added to the interlayer gelatin solution This will constitute a filter which absorbs light in the inherent sensitive portion of the spectrum of the sensitive emulsion layer coated immediately below the interlayer, and serve to render the color separation complete. (The dyestuflf is bleached during the treatment.)

Finally, on top of these two sets of combinations of the superposed multilayers, there is coated the last set of a combination of multilayers which is blue-sensitive and yellow-colored. The combination consists of a pre-fogged emulsion layer containing Brilliant Yellow (CI 24890), a non-color-sensitized inherently blue sensitive layer and a gelatin overlayer. The coating of these three sets of combinations is conducted usually by extrusion coating (three layers at a time) to obtain a final color paper.

This color paper is suitable for printing from a color negative. It is printed by a suitable printer, and then developed at first with the following back-and-white developing solution.

Developing solution:

p-Methylaminophenol sulfate g 1.5 Hydroquinone g 6.0 Sodium sulfite (anhydrous) g 80 Sodium carbonate (monohydrate) g 35 Water liter 1 After development, the print is treated with the following dye-bleach solution for 3 minutes.

Dye-bleach solution:

Thiourea g 200 Hydroquinone g 100 Hydrochloric acid (conc.) ml 20 Methyl alcohol ml 300 Water liter 1 Thereafter, it is rinsed thoroughly, and the remaining silver image is completely bleached with the following silver-bleach solution.

Silver-bleach solution:

A color paper is produced by coating three sets of combinations of superposed multilayers in the same manner as set forth in Example 3 except the following. Blau T pina" (trade name, Hoechst, Germany) is added as a blue dyestulf dischargeable during the treatment in an amount of about 0.5 g./m. to the red-sensitive emulsion layer of the first (bottom) set. To the green-sensitive layer of the second (middle) set about the same amount of a dischargeable magenta dye available under the tradename Karmin KE pina is added. About 0.7 g./m. of Pangelb pina (trade name) is also added to the noncolor-sensitized (blue-sensitive) emulsion layer of the topmost set. The amounts of the above dyestuflis incorporated in the emulsion layer are adjusted so that the color density of the emulsion layer at the maximum absorption is about 0.3-0.5.

By so doing, the irradiation of light during exposure is avoided efiiciently an dthe accutance (resolution) or the sharpness of the emulsion is much increased. An excellent color paper which has enough high resolution and much higher sensitivity for printing is obtained because the dyestutf concentration is not so high as in the conventional silver-dye-bleach paper. The printing and developing processes are the same as set forth in Example 3. The above dyestulfs are completely discharged during the treatment.

EXAMPLE 5 The procedure of Example 3 is repeated except that the silver chloride emulsion of Example 1 is used with out chemical fogging, in place of the 5% gelatin solution as an interlayer, and the coating amount of the emulsion is about 0.3 g./m. calculated as AgNO after having been diluted with a gelatin solution. A color paper of excellent color tone without any color mixing was obtained. The processing procedure used is the same as that set forth in Example 3. The silver chloride in the interlayer is completely discharged during the fixation.

EXAMPLE 6 The same procedure as set forth in Example 4 is followed except that an interlayer of the same composition as that used in Example 5, and the sets of multilayers are coated on a film base instead of the polyethylenecoated photographic base paper. A color microfilm with relatively high sensitivity and high resolving power is obtained. The film so obtained is able to prevent halation completely due to the presence of complementary colored layers under the emulsion layers in each set of combinations, and it is not necessary to use a gray base or the coating of special anti-halation layer.

What is claimed is:

1. A color photographic material for the silver dyebleach process comprising a support and at least two multilayer combinations, each of said multilayer combinations comprising (a) a pre-fogged chloride-rich silver halide emulsion layer containing a bleachable dye, (b) a high-speed bromide-rich silver halide emulsion layer which is sensitized to the spectrum of light complementary to said bleachable dye incorporated in said chloride-rich layer and which is superposed upon said pre-fogged chloride-rich layer; and (c) a binder layer superposed upon said high-speed bromide-rich layer, wherein the dye is different in each combination.

References Cited UNITED STATES PATENTS 2,996,3 82. 8/ 1961 Luckey 96-68 3,505,068 4/1970 Beckett 96-74 3,050,391 8/ 1962 Thompson 96--61 3,418,123 12/1968 *Haugh 9663 3,4505 36 6/ 1969 Wyckotf 966 8 FOREIGN PATENTS 726,137 1/ 1966 Canada.

818,687 8/1959 Great Britain.

923,045 4/ 1963 Great Britain. 1,175,753 12/ 1969 Great Britain.

NORMAN G. TORCHIN, Primary Examiner A. T. SURO PICC, Assistant Examiner US. Cl. X.R. 96-68 

